You make a big assumption here that drives your argument, but the point is if you lease the same car that you financed, your lease would be much less. That money could have gone to your homeloan immediately. So if we use your 3/5k example, if you are paying 5000pm currently, and were leased at 3000, you could have floated an extra 2k per month to your homeloan. Now I'm not saying in the specific example you would be better off if you leased, but again there is merit in leasing depending on how you buy and how you use the money you save.
That's obviously what I said and is the ideal. My point was rather to illustrate why people see it as a bad deal.
One thing to bear in mind when leasing though is that is that if you find yourself suddenly unemployed you sit with a much bigger problem than someone who is buying to own...or even better had already done so with no need to buy a new one.
Your notion of wanting to replace every two-three years is already leaning towards qualifying the leasing option to yourself as a least cost option.
You could have had the same car purchased over five years instead of the same installment and then owned it.
The drive for new every so often is just as bad as the one of paying the same cost for a better specced leased car over a purchase one.
Going by your logic I would be paying R3k per month perpetually to lease (and increasing with every car).
3k X 120 months = R360 000 into cars and only R240 000 into my house.
5k X 54 months on my bought to own car = R270 000 into car.
5k X 66 months that I don't need to pay a car = R330 000 into my house.
Therefore the need to replace every three years and to use leasing to accomplish this does sort of come to the conclusion that you can't really afford the specific car and/or lifestyle in the first place.
Well you can obviously afford it, but you could do better otherwise.
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Obviously the 3k & 5k were never real numbers but I'm quite sure the above calculation will probably hold even more true with real numbers.